that marvellous pre-established harmony between the soul and the body, and indeed amongst all the monads or simple substances, which takes the place of an untenable influence of one on another and, in the opinion of the author of the finest of dictionaries [Bayle], exalts the greatness of divine perfection beyond anything previously conceived. It would not be adding much to that if I said that it is these minute perceptions which determine 56 our behaviour in many situations without our thinking of them, and which deceive the unsophisticated with an appearance of indifference of equilibrium - as if it made no difference to us?for instance?whether we turned left or right. I need not point out here, since I have done so in the work itself [pp. 164Ñ6?i88f]t that they cause that disquiet which I show to consist in something which differs from suffering only as small from large, and yet which frequently causes our desire and even our pleasure, to which it gives a dash of spice. They are also the insensible parts of our sensible perceptions, which bring it about that those perceptions of colours, warmth and other sensible qualities are related to the motions in bodies which correspond to them; whereas the Cartesians (like our author, discerning as he is), regard it as arbitrary what perceptions we have of these qualities?as if God had given them to the soul according to his good pleasure, without concern for any essential relation between perceptions and their objects. This is a view which surprises me and appears unworthy of the wisdom of the author of things, who does nothing without harmony and reason.
  In short, insensible perceptions are as important to pneumatology as insensible corpuscles are to ^natural science, and it is just as unreasonable to reject the one as the other on the pretext that they are beyond the reach of our senses. Nothing takes place suddenly?and it is one of my great and best confirmed maxims that nature never makes leaps. I called this the Law of Continuity when I discussed it formerly in the Nouvelles de la republique des lettres [ Letter on a general principle useful in explaining the laws of natureÕ]. There is much work for this law to do in natural science. It implies that any change from small to large, or vice versa, passes through something which is?in respect of degrees as well as of parts, in between; and that no motion ever springs immediately from a state of rest, or passes into one except through a lesser motion; just as one could never traverse a certain line or distance without first traversing a shorter one. Despite which?until now those who